Removal of elemental sulfur and mercaptan (thiol) contaminants is a frequently encountered problem in the petroleum industries. Some sulfur contaminants such as elemental sulfur are difficult to remove. Others such as mercaptans are very reactive. However, existing sulfur removal methods only often dimerize mercaptans into disulfides. See, e.g. U.S. Pat. No. 5,169,516. The disulfides remain in the hydrocarbon, failing to achieve the goal of sulfur removal. The problem is even more difficult to solve if the hydrocarbon stream contains reactive unsaturates such as acetylenes, diolefins, olefins or aromatics.
Metal oxides and metals, including of the Metal Groups IB, IIB and IIIA, have been used in processes seeking to remove sulfur and sulfur containing compounds. Metal oxides of copper (Group IB) and zinc (Group IIB) have long been used to remove hydrogen sulfide (e.g. ZnO+H.sub.2 S&gt;ZnS+H.sub.2 O). See, for example, U.S. Pat. Nos. 2,959,538, 3,660,276, 4,314,902, 4,978,439, 5,106,484; cf U.S. Pat. No. 5,130,109. Metallic copper or zinc has been used in certain circumstances, normally involving elevated temperatures, in sulfur and sulfur compound removal. For example, see: U.S. Pat. No. 2,768,932 (contacting a hydrofixed, sulfur-containing petroleum distillate with finely divided metallic copper, copper alloys and copper oxides at elevated temperatures up to about 350.degree. C.); U.S. Pat. No. 2,897,142 (contacting a hydrodesulfurized petroleum distillate boiling in the range between 300.degree. F. to 400.degree. F. 149.degree. C.-204.degree. C.! with free copper or silver in the absence of hydrogen); U.S. Pat. No. 3,145,161 (contacting a neutralized, acid treated distillate oil with copper metal at 100.degree. F. to 500.degree. F. 38.degree. C. to 260.degree. C.!); U.S. Pat. No. 3,945,914 (contacting an oxidized sulfur-containing hydrocarbon material with copper or zinc at a temperature from 500.degree. F. to 1350.degree. F. 260.degree. C. to 732.degree. C.!); U.S. Pat. No. 4,113,606 (contacting a refined hydrocarbon feed with particulate copper, iron or zinc or compounds thereof or composites of them and refractory oxides of Groups II to IV metals supported in a binder of a refractory material and having a surface area of 2 to 700 m.sup.2 /gm); U.S. Pat. No. 4,163,708 (contacting a hydrodesulfurized hydrocracked oil in the absence of molecular oxygen and at a temperature of 120.degree. C. to 400.degree. C. with a composite of a copper or copper compound component and a porous carrier having a surface area of 20 to 1000 m.sup.2 /gm); U.S. Pat. No. 4,204,947 (absorbing and removing thiol impurities from hydrocarbon oils by contacting the oil in the absence of molecular oxygen with a scavenger at a temperature in the range of about 120.degree. to 400.degree. C.) and U.S. Pat. No. 5,173,173 (contacting feedstock containing naphtha or jet fuel with copper components supported on an alumina-containing porous refractory oxide at temperatures from 200.degree. F. to 700.degree. F. 93.degree. C. to 371.degree. C.! under sulfur absorption conditions, including absence of free hydrogen).
However, none of this art is directed to the problem of removing elemental sulfur or mercaptans from highly unsaturated reactive hydrocarbons especially rich in aromatics, olefins, diolefins or acetylenes. Indeed the art contra-indicates possible use of metallic copper or copper oxides for sulfur or mercaptan removal from highly reactive hydrocarbons: copper on a support is taught used as a catalyst for selective hydrogenation of acetylenes in the presence of butadienes; see U.S. Pat. Nos. 4,440,956, 4,493,906. And at temperatures from 200.degree. F. to 260.degree. F. 93.degree. C. to 127.degree. C.! and in the absence of free hydrogen, copper oxide or silver oxide is employed to crack acetylenes in a hydrocarbon stream in which a polymerization inhibitor is used to also prevent polymerization of butadienes. Conditions that include elevated temperature are unsuitable for removal of sulfur and mercaptans from highly reactive hydrocarbons, because at elevated temperatures unsaturated hydrocarbons tend to oligomerize and polymerize, especially the very labile alkyne and diolefin components such as acetylene and butadiene.
My invention is directed to the goal of an effective technique for sulfur and mercaptan removal which does not rely upon operating conditions that involve substantially elevated temperatures, but instead may be conducted at mild conditions, thereby lending the method to application for treating reactive hydrocarbon streams such as butadiene and acetylene.